1. Field of the Invention
The present invention relates to a peer to peer (P2P) information delivery system including a plurality of node devices connected with each other via a network and method or the like thereof and, especially, relates to a technical field for a non-participating node device to participate in an overlay network which is formed by participation of all or part of the plurality of node devices.
2. Discussion of Related Art
In the peer to peer information delivery system, for example, in an overlay network which is logically configured by use of a distributed hash table (hereinafter referred to as DHT), each of node devices which participates in the overlay network does not recognize link information (for example, IP address) of all the node devices, but retains only part of link information obtained on participation or the like and data inquiry or the like is performed on the basis of such link information.
In an overlay network thus structured, it is necessary that distribution of load be appropriately performed even when participation and withdrawal of node devices occur often. In Non-patent Document 1, a technique which enables appropriate distribution of load even when participation and withdrawal often occur is disclosed.
Non-patent Document 1: “Lightweight Load Balancing for Distributed Hash Table”. Technical Report of the Institute of Electronics, Information, and Communication Engineers.
However, in the above conventional technique, locality, in other words, distance in a real network, is not considered with regard to link information of each of node devices. Therefore it is considered whether or not unnecessary load should be given to a real network.